Dual antenna wireless communication device in a load control system

Abstract

A wireless communication device for use in a load control system for controlling one or more electrical loads may comprise a counterpoise, a first and second antennas, a RF communication circuit and a control circuit. The two antennas may be oriented differently and spaced apart from each other. For example, the first antenna may extend perpendicularly from the counterpoise while the second antenna extends in a plane substantially parallel to the counterpoise. The first antenna may extend from the counterpoise at a point substantially central to the counterpoise while the second antenna may extend along a perimeter of the counterpoise. The RF communication circuit may transmit wireless signals via the first and second antennas. The control circuit may cause the RF communication circuit to transmit a first wireless signal in a first time slot and a second wireless signal in a second time slot.

What is claimed is: 
     
       1. An antenna structure comprising:
 an electrically conductive, planar, counterpoise having a physical geometry forming a perimeter; 
 a first antenna galvanically coupled to the counterpoise and disposed about at least a portion of the perimeter of the planar counterpoise, the first antenna having a first end coupled to a first transceiver and an ungrounded second end; and 
 a second antenna galvanically coupled to the counterpoise, the second antenna having a first end coupled to a second transceiver and an ungrounded second end;
 wherein the counterpoise provides a common RF ground for the first antenna and the second antenna; and 
 wherein the first antenna and the second antenna comprise polar diverse antennas. 
 
 
     
     
       2. The antenna structure of  claim 1  wherein the counterpoise and the first antenna form coplanar structures. 
     
     
       3. The antenna structure of  claim 1  wherein the second antenna comprises an antenna disposed orthogonal to the planar counterpoise. 
     
     
       4. The antenna structure of  claim 1  wherein the planar counterpoise comprises a circular planar counterpoise. 
     
     
       5. The antenna structure of  claim 4  wherein the second antenna comprises an antenna that penetrates the planar counterpoise and is disposed orthogonal to the planar counterpoise. 
     
     
       6. The antenna structure of  claim 5  wherein the second antenna penetrates the circular planar counterpoise at the center point of the circular planar counterpoise. 
     
     
       7. The antenna structure of  claim 1  wherein the counterpoise comprises a plurality of stacked, electrically conductive, layers. 
     
     
       8. The antenna structure of  claim 7  wherein the counterpoise comprises a printed circuit board that includes the plurality of stacked, electrically conductive, layers forming the counterpoise. 
     
     
       9. The antenna structure of  claim 1  wherein the first antenna and the second antenna are physically separated by less than a quarter of a wavelength of the transmission frequency of the first antenna and the second antenna. 
     
     
       10. The antenna structure of  claim 1  wherein the second antenna comprises a helical antenna. 
     
     
       11. The antenna structure of  claim 1  wherein a radio-frequency isolation between the first antenna and the second antenna is greater than 15 decibels (dB). 
     
     
       12. The antenna structure of  claim 1  wherein the first antenna includes a jumper to adjust the length of the first antenna to change the transmission frequency of the first antenna.